1. Field of the Invention
The present invention relates to the field of magnetic resonance imaging and more specifically to the field of imaging moving matter with magnetic resonance.
2. Description of Related Art
Motion, particularly that of fluids, is an important parameter in many systems. Information of the gradients in velocity and acceleration is useful in design and analysis of fluid flow systems. Gradients in velocity and acceleration indicate regions of potential turbulence, and stagnant areas. These may lead to corrosion in metal pipes, areas of blockage, etc. Also, regions of slow flow through vessels of living subjects have been shown to play a central role in the in-vivo development of arteriosclerotic disease.
A traditional fluid flow analysis method, known as ink streamlining, requires introducing a contrast agent into a flowing fluid and observing the motion of the contrast agent.
Another method of measuring motion of materials employs laser Doppler technique. This requires a laser beam to be reflected from particles suspended in the material which is to be measured, and determining the displacement of each particle over a short interval thereby indicating the velocity of the material at the chosen location.
Both of these methods are invasive, or destructive, and require direct access to the material being tested. If the material is in inside a tube or deep within a living subject, these methods will not be useful. Furthermore, they are not suited for in-vivo, or non-destructive testing applications.
A number of methods for the detection and measurement of fluid motion with magnetic resonance have been previously disclosed. These methods use either a bolus tracking approach in which the magnetization of a bolus of moving fluid is changed and followed, or they use approaches in which motion encoding magnetic field gradient pulses are used to induce a phase shift which is proportional to a desired component of motion such as velocity, acceleration and jerk. Prior methods for the detection of motion with magnetic resonance are limited in their application since only a single component of motion can be detected at a time.
It would be useful to have a method which non-invasively measures several components of motion simultaneously.